Combine the Base: Find a clean glass jar with a secure, tight-fitting lid. A jam jar works wonderfully. Add the red wine vinegar, Dijon mustard, sugar (if using), salt, and black pepper to the jar.

Mix the Base: Screw the lid on tightly and give the jar a good shake for about 10 seconds. This helps the salt and sugar dissolve into the vinegar before you add the oil.

Add the Oil: Pour the extra virgin olive oil into the jar with the vinegar mixture.

Emulsify: Secure the lid tightly again. This is the important part! Shake the jar vigorously for about 30-45 seconds. You should see the mixture transform from two separate layers into a single, creamy, and slightly thickened dressing. What works best for me is to shake it until I can no longer see any distinct oil droplets.

Taste and Adjust: Unscrew the lid and dip a piece of lettuce or your finger in to taste. It might need a little more salt or pepper. If it's too sharp for your liking, add another tablespoon of olive oil and shake again. If it tastes a bit flat, a tiny splash more vinegar can brighten it up.

Serve or Store: You can use the dressing immediately, or store it in the fridge. Just remember to give it another good shake right before serving.